<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>固定定位</title>

        <style>
            .fu{
                background-color: #ff0;
                width: 500px;
            }
            .fu>div{
                width: 100px;
                height: 100px;
            }
            .z1{
                background-color: #f00;
            }
            .z2{
                background-color: #0f0;
                /* 固定定位 */
                position: fixed;
                right: 0;
                top: 0;
            }
            .z3{
                background-color: #00f;
            }
        </style>

    </head>
    <body>
        <div class="fu">
            <div class="z1">z1</div>
            <div class="z2">z2</div>
            <div class="z3">z3</div>
        </div>

    </body>
</html>